@jwilliams89 From my experience, the radiators were sized correctly. I have 5 (I think) large K3s downstairs. One is 84Kg empty, so you need something solid to hang them off(!)

@iancalderbank This is fantastic thanks. I'll talk to the installers when they come in. My inkling is that talking to the office achieves nothing. If I need to buy the extra valves myself that would, as you say, be much better than having to redo it all. I wonder if the most difficult part would be getting them to provide a fully sized/powered pump.

Do you know if a full zone could be run from 22mm pipe or would it need 28mm? I guess that is the only thing as they are only speccing 22mm.

@allyfish This sounds positive, although the chances of getting the eco 4 company to come back and retrofit seem like they would be zero. Shame this isn't already in effect!

I'm looking at how I can get the installers to properly balance the primary and secondary. I'll look back through the archives but if you can point me in the right direction I'd appreciate that.

@mikefl What rough size is your house? We have an open plan downstairs which they are talking about putting two large radiators and one smaller one in. Upstairs will have large radiator in each of three bedrooms and one in the bathroom. I'm trying to get them to change to 1 large and three medium downstairs as 2 large will take up all our wall space on one side. Also trying to get them to put one on the landing upstairs.

@jwilliams89 

depends on a) how big your system / zone is and b) how far away / how long the pipe run! 

how big your system / zone is:

Most "rule of thumb" plumbers would put in 28mm from source to distribution point (where cylinder is , where zone valve switching is) and 22mm to emitter zones. A HP may need an uplift on pipe sizes due to the flow rate (28 to 35, 22 to 28) or may not  - the size of the heat input required is what determines this.

see this table:

DT5 is the standard number for a heat pump. 0.9 m/sec is the flow velocity in any one pipe that a good pipework design should aim to stay under.

figures are in kW and show the max kW that each size pipe (copper) can carry without exceeding 0.9 m/sec. The kW figure is the one that you work out - how many kW of emitters will be hanging off that pipe. At the flow rate and flow temp needed for a heat pump in design conditions - not based on radiator spec sheet "DT50" kW value.

Table  comes from here https://www.heatgeek.com/does-my-pipework-need-upgrading-for-a-heat-pump-with-cheat-sheet/

how long the pipe run:

• work out how long it is in M and the flow rate it needs to support (which comes from the Kw and the DT)
• then stick the values into the metric calculator in here https://www.engineeringtoolbox.com/hazen-williams-water-d_797.html
• try the inner pipe sizes for 22mm and 28mm . the specific head loss comes out in mm.

domestic circulating pump may have a head of around 5-10M (depending on spec ) so 5000 - 10000mm. If maths tells you one pipe run is costing you 4000mm of head at the flow rate it needs to carry, that pipe is too small. If it costs 40mm of head, its a big enough pipe and you can ignore it.

if they quote your for two pumps with 5M head, ask for one of them to be uplifted to  bigger one. 

28mm full bore valves are 12 quid each:

https://www.monsterplumb.co.uk/red-blue-butterfly-tbar-ball-valve-28mm?gclid=CjwKCAiAg9urBhB_EiwAgw88mZkNcec2WTJvtBOY7HNpCzCMl7UJrOkUCY40OL2_O1qNiwrE3HHvxBoCA-AQAvD_BwE

regarding my diagram I drew for a way to convert - if doing this, build it so that the pipe route when bypassing the LLH is the straight line. the "diversion route" with the Tees and elbows into the LLH. i.e not the way round I drew it. every elbow costs a little bit of head loss and when building a single loop you want as straight as you can.

@jwilliams89 a landing rad is a really good idea. you may want to turn down your bedroom rads if you prefer cooler to sleep. having a landing rad keeps an emitter open moving heat into the upstairs.

Posted by: @jwilliams89

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@mikefl What rough size is your house? We have an open plan downstairs which they are talking about putting two large radiators and one smaller one in. Upstairs will have large radiator in each of three bedrooms and one in the bathroom. I'm trying to get them to change to 1 large and three medium downstairs as 2 large will take up all our wall space on one side. Also trying to get them to put one on the landing upstairs.

For maximum overall efficiency the heat emitter capacity should be as large as possible, but also balanced as closely as possible to the heat loss of individual rooms.

@jwilliams89 The house is around 150m2, split 110/40 (it's a converted bungalow, which is why the split is so unbalanced). Hence the K3s are downstairs, and upstairs are just the original K2s. In my case, I feel zoning wasn't a good decision, due to this large imbalance.

@jwilliams89 Likely under ECO4 the installers will fit the Grant Chofu controller, which comes as standard with the Aerona. The smart controller hasn't launched yet, and at an additional cost premium. What I would try and persuade them to do is fit flow setting valves on primary and secondary sides of any LLH. As standard you'll get one on the primary side only. Then you have to measure temperatures in and out to balance, whereas with adjustment valves on both sides it's easy to find the optimum pump speed setting - that's basically whichever setting requires least closing of the flow setter valves, as the valves are just a restriction and system inefficiency. Last thing you want to do is have the primary pump on full speed against a nearly closed setting valve to drop the flow down. Equal flow on primary and secondary sides, or equal temperature across the LLH means it is balanced.

@allyfish That all makes total sense. I'm hoping if I feed the installers bacon butties and offer to pay for any extra valves they'll adjust the system for me. Is it normal to site the chorfu controller with the tank (in this instance in the loft)? If they won't site it downstairs so I can access and use it properly I'm looking into how easy it is for me to extend the wiring the move this myself.

@iancalderbank Yeah that was my thinking. I'm going to at least insist of plumbing to the landing and I'll provide an extra rad myself if need be. What is the received wisdom on vertical rads? They will fit one if I provide it, but I don't want to go down that route if vertical rads aren't capable enough for the space.

Posted by: @jwilliams89

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Is it normal to site the chorfu controller with the tank (in this instance in the loft)? If they won't site it downstairs so I can access and use it properly I'm looking into how easy it is for me to extend the wiring the move this myself

It's a two wire low voltage DC device powered from the ASHP. Grant tend to hide them away with the tank and use the primary side piping route to run the control cable. As it's SELV you can relocate it yourself if they won't put it somewhere sensible. I would hope they would not put it in a loft if access isn't a fixed stairs, because that's far from ideal for you.